When Sirio came out with their Al. sleeve engines, a lot of people had problems with the sleeves breacking prematurely, the same thing happend when Novarossi came out with their 421p Al sleeve engines. Someone on the forum mentioned that the problem was that the sleeve would get loose on the case and vibrate, causing it to break.
AKA El Pibe RUFAST? HAHA!!!
Ronin Speed Parts